import re
import sys
from functools import wraps
from inspect import getmembers
from types import CoroutineType
from typing import AsyncGenerator, Dict
from unittest import TestCase

from scrapy.http import Request
from scrapy.utils.python import get_spec
from scrapy.utils.spider import iterate_spider_output


class Contract:
    """Abstract class for contracts"""

    request_cls = None

    def __init__(self, method, *args):
        self.testcase_pre = _create_testcase(method, f"@{self.name} pre-hook")
        self.testcase_post = _create_testcase(method, f"@{self.name} post-hook")
        self.args = args

    def add_pre_hook(self, request, results):
        if hasattr(self, "pre_process"):
            cb = request.callback

            @wraps(cb)
            def wrapper(response, **cb_kwargs):
                try:
                    results.startTest(self.testcase_pre)
                    self.pre_process(response)
                    results.stopTest(self.testcase_pre)
                except AssertionError:
                    results.addFailure(self.testcase_pre, sys.exc_info())
                except Exception:
                    results.addError(self.testcase_pre, sys.exc_info())
                else:
                    results.addSuccess(self.testcase_pre)
                finally:
                    cb_result = cb(response, **cb_kwargs)
                    if isinstance(cb_result, (AsyncGenerator, CoroutineType)):
                        raise TypeError("Contracts don't support async callbacks")
                    return list(iterate_spider_output(cb_result))

            request.callback = wrapper

        return request

    def add_post_hook(self, request, results):
        if hasattr(self, "post_process"):
            cb = request.callback

            @wraps(cb)
            def wrapper(response, **cb_kwargs):
                cb_result = cb(response, **cb_kwargs)
                if isinstance(cb_result, (AsyncGenerator, CoroutineType)):
                    raise TypeError("Contracts don't support async callbacks")
                output = list(iterate_spider_output(cb_result))
                try:
                    results.startTest(self.testcase_post)
                    self.post_process(output)
                    results.stopTest(self.testcase_post)
                except AssertionError:
                    results.addFailure(self.testcase_post, sys.exc_info())
                except Exception:
                    results.addError(self.testcase_post, sys.exc_info())
                else:
                    results.addSuccess(self.testcase_post)
                finally:
                    return output

            request.callback = wrapper

        return request

    def adjust_request_args(self, args):
        return args


class ContractsManager:
    contracts: Dict[str, Contract] = {}

    def __init__(self, contracts):
        for contract in contracts:
            self.contracts[contract.name] = contract

    def tested_methods_from_spidercls(self, spidercls):
        is_method = re.compile(r"^\s*@", re.MULTILINE).search
        methods = []
        for key, value in getmembers(spidercls):
            if callable(value) and value.__doc__ and is_method(value.__doc__):
                methods.append(key)

        return methods

    def extract_contracts(self, method):
        contracts = []
        for line in method.__doc__.split("\n"):
            line = line.strip()

            if line.startswith("@"):
                name, args = re.match(r"@(\w+)\s*(.*)", line).groups()
                args = re.split(r"\s+", args)

                contracts.append(self.contracts[name](method, *args))

        return contracts

    def from_spider(self, spider, results):
        requests = []
        for method in self.tested_methods_from_spidercls(type(spider)):
            bound_method = spider.__getattribute__(method)
            try:
                requests.append(self.from_method(bound_method, results))
            except Exception:
                case = _create_testcase(bound_method, "contract")
                results.addError(case, sys.exc_info())

        return requests

    def from_method(self, method, results):
        contracts = self.extract_contracts(method)
        if contracts:
            request_cls = Request
            for contract in contracts:
                if contract.request_cls is not None:
                    request_cls = contract.request_cls

            # calculate request args
            args, kwargs = get_spec(request_cls.__init__)

            # Don't filter requests to allow
            # testing different callbacks on the same URL.
            kwargs["dont_filter"] = True
            kwargs["callback"] = method

            for contract in contracts:
                kwargs = contract.adjust_request_args(kwargs)

            args.remove("self")

            # check if all positional arguments are defined in kwargs
            if set(args).issubset(set(kwargs)):
                request = request_cls(**kwargs)

                # execute pre and post hooks in order
                for contract in reversed(contracts):
                    request = contract.add_pre_hook(request, results)
                for contract in contracts:
                    request = contract.add_post_hook(request, results)

                self._clean_req(request, method, results)
                return request

    def _clean_req(self, request, method, results):
        """stop the request from returning objects and records any errors"""

        cb = request.callback

        @wraps(cb)
        def cb_wrapper(response, **cb_kwargs):
            try:
                output = cb(response, **cb_kwargs)
                output = list(iterate_spider_output(output))
            except Exception:
                case = _create_testcase(method, "callback")
                results.addError(case, sys.exc_info())

        def eb_wrapper(failure):
            case = _create_testcase(method, "errback")
            exc_info = failure.type, failure.value, failure.getTracebackObject()
            results.addError(case, exc_info)

        request.callback = cb_wrapper
        request.errback = eb_wrapper


def _create_testcase(method, desc):
    spider = method.__self__.name

    class ContractTestCase(TestCase):
        def __str__(_self):
            return f"[{spider}] {method.__name__} ({desc})"

    name = f"{spider}_{method.__name__}"
    setattr(ContractTestCase, name, lambda x: x)
    return ContractTestCase(name)
